In 1883, the Krakatoa volcano in Dutch Indonesia
erupted. The resulting explosion blew the whole
mountain away, and the smoke from the eruption
reached the stratosphere and subsequently was carried
along the equator, around the world in 13 days in
a westward direction. As the smoke cloud covered
the sun, it was said to have turned a blue-green
color. From the direction the cloud was carried at
the time, it was thought that

an
easterly

wind blows in the stratosphere above the equator.
This wind is called the Krakatoa Easterly.

However, 25 years later in 1908, when Berson
carried out balloon sounding near Lake Victoria in
Africa, the wind in the stratosphere above the
equator was

a westerly.

This is called the Berson Westerly. In
exactly what direction is the air above the equator
blowing?